Electromagnetic bell striker actuating assembly



June 30, 1964 w. E. LEVINE 3,139,565

ELECTROMAGNETIC BELL. STRIKER ACTUATING ASSEMBLY Filed 001:. 4, 1960 2 Sheets-Sheet 1 INVENTOR. WALTER E. LEVINE ATTORNEYS June 0, 1964 w. E. LEVINE 3,139,565

ELECTROMAGNETIC BELL STRIKEIR ACTUATING ASSEMBLY Fil 1960 2 Sheets-Sheet 2 FIG. 9

IN VEN TOR.

WALTER E. LEVINE United States Patent 3,139,565 ELECTROMAGNETIC BELL STRIKER ACTUATING ASSEMBLY Walter E. Levine, I-Iamden, Conn., assignor to Edwards Company, Inc., a corporation of Connecticut Filed Oct. 4, 1960, Ser. No. 60,326

1 Claim. (Cl. 317-172) This invention relates to a bell striker actuating assembly of the type in which a striker plunger is caused to reciprocate and strike a gong for generating audible signals by means of the coaction between a permanent magnet and an electromagnetic coil.

, In the type of structure to which this invention relates the bell striker plunger is slidably mounted in a nonmagnetic tube which in turn carries an electromagnetic coil that surrounds the tube. A permanent magnet is mounted in spaced relationship to the electromagnetic coil and pole pieces are employed for conducting the flux of the permanent magnet into the bore of the tube which causes the plunger to compress a spring and provide potential energy for reciprocating the plunger. When alternating current is supplied to the electromagnetic coil the flux of the coil alternatively opposes and aids the flux of the permanent magnet causing the striker plunger to reciprocate and strike a gong and generate audible signals. Such a structure is described in Fish Patent No. 2,561,355 and as there described the use of the flux of the permanent magnet materially increases the efiiciency of bells employing an electromagnetic coil with alternat ing current. While the type of structure described in the Fish patent has proven commercially satisfactory, in working with the structure it has now been found that the flux ofthe permanent magnet is not etficiently utilized. In the Fish structure the permanent magnet is spaced away from the electromagnetic coileither off to one side of the axis of the coil or when arranged coaxially it is positioned adjacent the coil. In both cases the arrangement is such that the flux of the permanent magnet is conducted to the bore of the tube by pole pieces which provide a flux path outside the confines of the coil which is quite long and only a portion of the flux of the permanent magnet is utilized. The permanent magnet is however, only subjected to a very limited portion of the alternating flux of the electromagnetic coil and this tends to preserve the strength of the permanent magnet. Furthermore, the intensity of the magnetic flux around the bore of the tube in the Fish structure is not uniform, there being a substantially higher flux intensity on one side of the tube as compared to the opposite side. This pulls the striker plunger out of axial alignment with the bore of the tube so that during its movement there is a frictional drag exerted on the plunger by the wall of the tube which reduces the plungers speed and impact force on the gong. I

It has now been discovered that the efiiciency of the unit may be materially improved by surrounding the electromagnetic coil with a permanent magnet in the form of a hollow cylinder that fits over the exteriorof in the magnetic strength of the permanent magnet caused by positioning it in the alternating flux of the electrooperation. In addition, the intensity of the magnetic 3,139,565 Patented June 30, 1964 flux around the bore of the nonmagnetic tube in the structure of this invention is completely uniform so that the striker plunger at all times moves freely through the tube in axialalignment therewith andmaximum impact between the plunger and the gong is achieved. The structure of the present invention is also extremely compact and cost of manufacture has been reduced.

These and other advantages and details of the structure of the present invention are best understood by reference to the accompanying drawings in which FIG. 1 illustrates the way in which the bell striker actuating assembly is mounted under a gong.

FIGS. 2 and 3 illustrate a convenient form of mount for the assembly of FIG. 1. 7

FIG. 4 is taken on line 4-4 of FIG. 1 to show the detailed construction of the bell striker assembly.

FIG. 5 illustrates the hollow cylindrical permanent magnet with pole piece as shown in FIG. 1.

FIG. 6 illustrates another form of the structure of FIG. 4.

FIGS. 7, 8 and 9 illustrate modified forms of'the bell striker assembly of FIG. 4. i

The preferred form of bell striker actuating assembly shown in FIGS. 1 through 4 comprises a tube of non- .magnetic material 12 which may be made of stainless the form of a hollow cylinder 20 is mounted to fit over the exterior of the electromagnetic coil 16 and a second pole piece of paramagnetic material in the form of a circular washer 22 is mounted on tube 12 adjacent the end of the electromagnetic coil 16. The diameter of the pole pieces 14 and 22 are preferably equal to the outside diameter of the cylindrical permanent magnet 20. For convenience of assembly the bore through pole pieces 14 and 22 and through spool piece 18 are made small enough to provide a tight frictional force fit with the exterior of tube 12 so that once these elements are assembled on the tube they will remain in fixed position thereon. If desired, additional locking means may be employed such as the conventional spring steel locking washers 24 and 26 which may be positioned on tube 12 to bear against the pole pieces at opposite ends of the assembly to assist in holding it in position on tube 12.

A paramagnetic steel striker plunger 28 is slidably mounted in the nonmagnetic tube 12. The body portion of the plunger has an outside diameter a few thousandths of an inch less than the. inside diameter of the tube so that the. plunger will slide freely in the tube. The nose 30 at one end of the plunger may if desired be made of nonmagnetic material. A pin 32 which projects out from magnetic coil is outweighed by increased efliciency of 7 the second end of the plunger is adapted to engage the apex of a paramagnetic'steel spring 34 which is seated against the shoulder of an annular flange 36 formed by turning in the rim of tube 12. 7 Pole piece 14 is provided with a small opening 38 so that the conductors 40 and 42 of the electromagnetic coil may be connected to a suitable source of alternating current (not shown) for the electromagnet. p I

A portion of the path of the magnetic flux of the cylindrical permanent magnet 20 is illustrated in FIG. 5. As there shown the flux of the permanent magnet travels through the pole piece 22 and the intensity of the flux entering tube 12 is uniform throughout the 360 circle a of the pole piece. The flux of the cylindrical permanent magnet passes across the gap'of the nonmagnetic tube 12 into the body portion of plunger 28 and then to the right in FIG. 4 where the'flux again passes across the gap of the nonmagnetic tube 12 and into pole piece 14. As in the case of pole piece 22 the intensity of the flux passing from the enlarged body portion of plunger 28 is uniform throughout the 360 circular opening in pole piece 14. The force of the flux in passing from pole piece 22 to the body of the plunger 28 and from the body of the plunger 28 to the pole piece 14 causes the plunger to move to the right in FIG. 4 and hold spring 34 under compression in the position shown in FIG. 4.

When alternating current is supplied to the electromagnet 16 the alternating current causes the flux of the electromagnet to aid and then oppose the flux of the permanent magnet. When the flux of the electromagnetic coil aids the flux of the permanent magnet plunger '28 is moved to the right in FIG. 4 to further compress spring 34. When the alternating flux of the electromagnetic coil opposes the flux of permanent magnet 2t) the spring and flux of the electromagnetic coil causes the plunger to move to the left in FIG. 4 and strike the gong. The alternating flux of the electrornagnetic coil causes the plunger to reciprocate in tube 12 and generate audible signals.

The structure of the present invention is extremely compact and may readily be mounted under a gong as best shown in FIG. 1. Any convenient mounting means may be employed. As shown in FIGS. 1 through 3 the mounting means may comprise a generally U shaped strip preferably of nonmagnetic material 44 having attachment flanges 46 and 43 positioned at opposite ends of the opening in the U. Strip 44 may be mounted on a suitable base 50 by means of screws 52 which pass through suitable openings in the attachment flanges. The bell striker actuating assembly of the present invention is then most conveniently mounted under the U shaped strip by means of a strap 54. Strap 54 comprises a generally U shaped strap having a pair of mounting flanges 56 and 58 positioned at the free ends of the U. A pair of screws not shown are inserted through suitable holes in the mounting flanges 56 and 58 respectively and then the screws are tightened into the threaded holes positioned in the cars so and 62 of the mounting strip 44. This positions assembly .under strip 44 with tube 12 projecting through a pair of holes 64 and 66 respectively in the legs of strip 44. A gong 68 is mounted on the top of the mounting strip 44 by means of the screw 71) which is engaged in the threaded hole 72 of mounting strip 44 to secure the gong in position with the lower portion of the gong hole opposite the nose 30 of the striker plunger 28. Any other convenient means of mounting the bell striker actuating assembly of the present invention under or adjacent to a gong may of course be employed. In the preferred form of structure shown spring 34 is a tapered non-linear spring but linear springs of uniform turn diametermay be employed and the spring may be made of nonmagnetic material if desired.

prongs are covered with suitable electrical insulating material where they pass through the holes in the pole piece and the distance between prongs 74 is such that they may be fitted into a conventional electric socket. For this purpose pole piece 80 is mounted at one end of tube 12. Otherwise the construction and operation of the structure of FIG. 6 is identical with that of FIG. 4.

The modified form of structure shown in FIG. 7 is of substantially identical construction with that shown in FIG. 4 with the exception that a flux guiding sleeve 82 of paramagnetic material is mounted on the exterior of tube 12 in order to intensify the magnetic flux within the bore of the tube and the electromagnetic coil 84 may be a so-called basket weave which eliminates the need for The form of structure shown in FIG. 4 may be readily made waterproof for marine use it being only necessary to apply a conventional proofing compound to the junction between the pole pieces, permanent magnet and nonmagnetic tube. The opening for the conductors of the electromagnetic in pole piece 14 may be conveniently waterproofed with conventional potting compound. When mounted with the longitudinal axis of tube 12 in vertical position water will drain out of the tube through the opening in flange 36 and the opening also tends to equalize air pressure on both sides of the striker plunger during reciprocation which assists ease of reciprocation of the plunger. 7

FIG. 6 illustrates a modified form of the structure of FIG. 4. In this modified form of structure the conductors 40 and 42 of coil 16 are each connected to a metal prong '74 which are held in fixed position in a pair of openings '76 and 78 in the pole piece 80. The metal a conventional spool piece. The flux guiding sleeve of paramagnetic material 82 makes a forced fit with the exterior of the nonmagnetic tube 12 and the interior rim of the sleeve extends approximately one-third of the distance into the bore of the coil. A second sleeve of nonmagnetic material 86 is positioned on the tube adjacent sleeve 82 and the sleeve 86 terminates at one end of the electromagnetic coil 84. As shown in the drawings the electromagnetic coil 84 is a basket weave type of coil which is mounted directly on the sleeves 82 and 86. Pole piece 88 is identical with pole piece 14 with the exception that the circular opening in the pole piece is adapted to fit tightly around the exterior of sleeve 82. As in the case of the structure of FIG. 4 a hollow cylindrical permanent magnet 20 is mounted on the exterior of the electromagnetic coil 84 and the pole piece 22 is then mounted on tube 12 adjacent the permanent magnet and electromagnetic coil. Otherwise the construction and operation of the structure shown in FIG. 7 is identical with that previously described in connection with FIG. 4. But as a result of the flux guiding sleeve 82 the gap between the permanent magnet and the enlarged body portion of the strtiker plunger 28 is positioned inside the bore of the electromagnet and this quite unexpectedly increased the efliciency of the unit.

The modified form of structure shown in FIG. 8 is identical with that shown in FIG. 7 with the exception that two flux guiding paramagnetic sleeves 92 and 94 respectively are positioned on the nonmagnetic tube 12 to extend into the bore of the electromagnetic coil 84 from opposite ends thereof. The flux guiding sleeves 92 and 94 each extend into the bore of the electromagnetic cail 34 approximately one-third of the length thereof. The two sleeves 92 and 94 are separated by means of a small sleeve 96 of nonmagnetic material as shown in the drawings. The two flux guiding sleeves tend to help to strengthen the magnetic flux within the bore of tube 12. Otherwise the construction and operation of the structure of FIG. 8 is identical with that described in connection with FIG. 7.

In the modified form of structure shown in FIG. 9 certain of the parts are reversed. As there shown the pole piece 28 is provided with a pole piece extension 10% having an enlarged portion 102 which is seated against the interior face of the pole piece. The pole piece extension passes through a suitable opening in the pole piece 98 and the extension is peened over as at 1614 to securely anchor the pole piece extension in positionin pole piece 98. A nonmagnetic tube 1% is forced over the enlarged portion 102 of the pole piece extension to securely anchor it in position thereon. As electromag netic coil 108 is mounted in position on the exterior of tube 106 adjacent pole piece 98. A permanent magnet 11b in the form of a hollow cylinder is mounted on the exterior of the electromagnetic coil 108. A second pole piece 112 is forced on the tube adjacent to the electromagnetic coil 198 and permanent magnet 110. The enlarged body portion 102 of the pole piece extension is provided with a pin 114 which extends out from the face thereof. The pin has a front head portion of nonmagnetic material which extends into the open end of the hollow cylindrical paramagnetic striker plunger 116. A linear Spring 118 having turns of uniform diameter is positioned on the pin 114 to bear against the rim of the cylindrical striker plunger 116 and against the face of the pole piece extension 102. The cylindrical striker plunger 116 has an outside diameter a few thousandths of an inch less than inside diameter of tube 106 so that the striker plunger is free to reciprocate in the tube. The second end of the plunger 116 is provided with a striker rod 119 preferably of nonmagnetic material which is adapted to strike a gong upon reciprocation of the plunger. If desired a bushing 120 of non-magnetic material such as nylon may be positioned in the open end of tube 166 to serve as a guide for striker rod 119.

The magnetic flux in this form of structure passes from the permanent magnetic 110 through pole piece 112 and then across the nonmagnetic tube 106 into the wall of the body of the cylindrical plunger 116. The flux of the permanent magnet then passes to the right in the wall ofplunger 116 and across the gap between the rim of the wall and the face of the pole piece extension 102. Thereafter the magnetic flux of the permanent magnet passes through pole piece 102 back to the permanent magnet. The flux of the permanent magnet causes the striker plunger 116 to move to the right in FIG. 9 to compress spring 118 as described in connection with the structure shown in FIG. 4.

The plunger is at rest as shown in FIG. 9 and actuation of the electromagnetic coil 108 by alternating current causes the plunger to reciprocate and generate audible signals as previously described in connection with the structureshown in FIG. 4.

It will be understood that it is intended to cover all changes and modifications of the preferred embodiments of structure herein chosen for the purpose of illustration which do not constitute a departure from the spirit and scope of the invention.

What is claimed is:

A reciprocating bell striker assembly comprising an electro-magnetic coil which is in the form of a hollow cylinder and is excited by alternating current, an axially polarized, hollow, cylindrical, permanent magnet mounted around the exterior of said electro-magnetic coil, two paramagnetic pole pieces which mount flush against opposite ends of said cylindrical permanent magnet to enclose said electro-magnetic coil within said permanent magnet and said pole pieces, said pole pieces each having a circular opening therethrough which is coaxial with the bore of said electro-magnetic coil so that said paramagnetic pole pieces conduct the magnetic flux of the permanent magnet and the electromagnetic coil into and out of said bore of the electromagnetic coil with approximately equal intensity 360 around the bore, a non-mag netic tube extending within said bore of the electromagnetic coil through the both openings in said pole pieces and having an obstruction at one end thereof, a spring positioned in the tube against said obstruction and a cylindrical paramagneticplunger positioned within said tube and bore of said electro-magnetic coil with one end thereof against said spring and in the proximity of one pole piece and the other end thereof extending out of said bore of the electro-magnetic coil through the other pole piece so that as the magnetic field through the bore of the electro-magnetic coil varies with alternating current flow through theelectro-magnetic coil the paramagnetic plunger will reciprocate back and forth within the tube with a minimum amount of friction between the interior wall of said tube and the side of the plunger.

References Cited in the file of this patent 'UNITED STATES PATENTS 2,561,355 Fish July 24, 1951 2,726,342 Caretto Dec. 6, 1955 2,915,681 Troy .2 Dec. 1, 1959 3,022,450 Chase Feb. 20, 1962 

